AY Honors/Fungi/Answer Key

1. Give the name of five classes of fungi and examples of each.

Chytridiomycota: The phylum Chytridiomycota, the chytrids, represents a group of primitive aquatic fungi. They are characterized by having gametes that are motile by means of flagella. Also some fungi reproduce sexual by Oospores this fungi are known as Oomycetes.

Zygomycota

The zygomycetes, in phylum Zygomycota, are characterized by the formation of sexual spores called zygospores. The zygospores are not contained within a specialized fruiting body or sac. Zygospores form when the haploid nuclei at the ends of two hyphae fuse together in a process of fertilization to form a diploid zygote. The zygote immediately undergoes meiosis to form haploid cells that develop into zygospores. The zygospores are unenclosed, or “naked,” between the parental hyphae. An example of a zygomycete is the common black bread mold, Rhizopus nigricans.

Glomeromycota

Members of the Glomeromycota are also known as the arbuscular mycorrhizal fungi. Only one species has been observed forming zygospores; all other species only reproduce asexually.

Ascomycota

The ascomycetes are members of the phylum Ascomycota. They are also called the “sac fungi” because their sexual spores (ascospores) are enclosed in tube-like sacs known as asci. The formation of ascospores is similar to that of zygospores, except that the ascospores formed by meiosis are enclosed in the asci. Neurospora crassa is an ascomycete mold that was important in studies of genetic linkage.

Basidiomycota

Basidiomycetes, also known as the “club fungi,” are classified in phylum Basidiomycota. Their sexual spores, or basidiospores, are formed on complex fruiting body structures called basidia. Basidiomycetes include some of the most complex fungi, including mushrooms and puffballs.

3. Name three important fungi and tell what their value is.

Saccharomyces cerevisiae: This fungus is used in baker's yeast.

Aspergillus niger: This fungus is used to make citric acid commercially, and it also can be used to make gluconic acid. Both are important food additives.

Penicillium chrysogenum: This is the organism that makes penicillin, from which the majority of the large class of beta-lactam antibiotics are derived. Penicillin and its derivatives have saved countless lives since they were discovered and isolated, starting in the 1940s.

4. Tell the life history of one example of each of the following:

a. Rust

The life histories of rusts often are mind-bogglingly complex, often with the fungus spending part of its life on one kind of plant, then another part on a completely different kind of plant. For example, near my trailer there's an Eastern Redcedar tree, Juniperus virginiana. All winter some brown, bumpy, woody, tumor-like items about the size of golfballs were visible growing on the branches. In early spring the bumps on the thing developed slender, sharp "horns" from which pollen-like dust emerged. You can see the item at the left, magnified about four times.

5. Identify five fungus plant diseases.

Fusarium oxysporum

Adventist Youth Honors Answer Book/Nature/Fungi/Fusarium oxysporum

Pinkroot

Pinkroot, Phoma terrestris.

Downy mildew

Adventist Youth Honors Answer Book/Nature/Fungi/Downy mildew

Botrytis leaf blight

Botrytis leaf blight, Botrytis squamosa.

Neck rot

Neck rot, Botrytis allii.

Smut

Smut, Urocystis cepulae.

Smudge

Smudge, Colletotrichum circinans.

White rot

White rot, Sclerotium cepivorum.

References

• http://www.caes.state.ct.us/PlantPestHandbookFiles/pphO/pphonio.htm